Frequency hopping reception may be used to reduce the effect of narrow band interfering signals. During frequency hopping reception the frequency of the reception band of a receiver is changed in successive hops. Thus reception bands at different frequencies are received respectively in successive time intervals. This has the effect that the distance between the reception band and the frequency of the interfering signal varies from time interval to time interval, only a few time intervals suffering strongly from the interference.
European Patent application No. 630106 describes a frequency hopping receiver. This document addresses the gain used in the receiver. An automatic gain control circuit is used, which adapts the gain to the observed signal strength. The document notes that the gain adaptation may be problematic due to amplitude changes at the transitions between time intervals with reception bands at different frequencies. This problem is addressed by imposing limits on the gain range of the automatic gain control during the time intervals. The limits may set dependent on the hops, so that different gain ranges can be used in different time intervals.
It has been found that interference may occur in such receivers even when the frequency of the reception bands stay away from the frequency of the interfering signal. Error correction circuitry typically corrects for such interference, but this reduces error correction capacity, or requires unnecessarily heavy error correction.